End mill chatter like crazy!!

[kuksul08]

I recently got a shiny new carbide end mill - 1/4" diameter, 1" flute length and 1" stickout, 2 flutes, standard helix, ER20 collet, and the darn thing chatters like crazy. I have never experienced this before with any of my tools to this degree. Usually a small tweak in feed/speed will cure it, but this is so bad I'm getting a rough nail-file like diagonal finish on my 6061 aluminum parts.

I'm running it anywhere from full slot to .010" WOC, 1/8" DOC, 4000RPM, 16IPM.

I've read some threads about how I need to load up the tool (0.020" chip load 😨) to get it to quiet down and smooth out, or slow it down to the 1000RPM range and keep my .005" chipload to get out of any harmonics that are occurring.

I'm thinking of staying with 3-flutes forever after this experience.

[A.K. Boomer]

3 flutes on aluminum is pretty good practice from what iv experienced but still you should not be getting this bad of results with two... do you have a geared head mill? could be setting up some nasty harmonics,,, I hate geared head mills - my step pulley belt drive has nothing but smooth elastics between the motor and the quill...

[754]

What rpm are you at ?and how much run out on shank of endmill

?

[kuksul08]

3 flutes on aluminum is pretty good practice from what iv experienced but still you should not be getting this bad of results with two... do you have a geared head mill? could be setting up some nasty harmonics,,, I hate geared head mills - my step pulley belt drive has nothing but smooth elastics between the motor and the quill...

It's a Tormach with a belt/pulley. Runs buttery smooth with any other tool.

I'm running 4000RPM. I will need to check the runout - good idea.

[tomato coupe]

1. 4000 RPM is slow for 1/4" carbide in aluminum - you should be at 15,000 or higher.
2. Your present chip load is only .002", not .005".
3. 1" flute length is pretty long for a 1/4" end mill.

[kuksul08]

My machine maxes out at 5k RPM so... 15k is not possible.

[tomato coupe]

My machine maxes out at 5k RPM so... 15k is not possible.

Yeah, that's why carbide end mills aren't that useful for hobbyists, especially in aluminum. You can't spin smaller end mills fast enough, and you don't have enough oomph to push the bigger end mills.

[A.K. Boomer]

.
3. 1" flute length is pretty long for a 1/4" end mill.

that part i do agree with --- as far as chip load and speed it depends on what he's using as coolant and don't think he mentioned that yet...

just something that's extra critical with aluminum unless your into that friction stir thing and the inevitable snapping sound...

[tomato coupe]

that part i do agree with --- as far as chip load and speed it depends on what he's using as coolant and don't think he mentioned that yet...

just something that's extra critical with aluminum unless your into that friction stir thing and the inevitable snapping sound...

The speed is too low, regardless of what type of coolant is used. 4000 RPM only gets him to about 250 fpm, and he needs to be in the 800-2000 range.

[JoeLee]

1. 4000 RPM is slow for 1/4" carbide in aluminum - you should be at 15,000 or higher.
2. Your present chip load is only .002", not .005".
3. 1" flute length is pretty long for a 1/4" end mill.

I don't know about that. I run carbide all the time on aluminum at RPM's less than 1000 and I get good finishes. It sounds more like something's loose.

JL.....

[A.K. Boomer]

I don't know about that. I run carbide all the time on aluminum at RPM's less than 1000 and I get good finishes. It sounds more like something's loose.

JL.....

Ditto on that - I use a mister and run it at 1550 and do just fine... In TC's defense im not production or anything - just trying to make things happen without wearing out my endmills or fuquing up my part and yeah good finishes unless I do something wrong,,, # 1 concern for me with aluminum is not letting it weld to the endmill - if i accomplish that one goal it seems most everything else works out...

[A.K. Boomer]

kuksul what are you using for coolant? did you inspect the endmills and make sure they are not holding little welded edges of aluminum?

will add - not uncommon for carbide to gall up in comparison to HSS --- in many cases HSS can be sharper and that can avoid welding problems...

[BCRider]

It sounds like you've done this before and not had any issues. For giggles how about check the X and Y gibs and just ensure that they are correctly snug. If it's been a while there may be a little wear causing some looseness.

And perhaps just check on the new end mill and make sure the shank isn't tapered. Not likely I know but it sounds like mostly you're looking at the unusual stuff outside of the usual.

[tomato coupe]

I don't know about that. I run carbide all the time on aluminum at RPM's less than 1000 and I get good finishes. It sounds more like something's loose.

Why are you running carbide that slow?

[tomato coupe]

I use a mister and run it at 1550 and do just fine -- just trying to make things happen without wearing out my endmills ...

If you're running 1/4" carbide end mills at 1500 RPM, you're actually shortening their life.